The present invention relates to a semiconductor device and its manufacturing method, and in particular, to a semiconductor device which has a capacitative element in which tantalum oxide (Ta2O5) is employed for a capacitative insulating film and its manufacturing method.
In a manufacturing method of a semiconductor device of this kind, high permittivity Ta2O5 has been employed for a semiconductor device having a capacitative element (DRAM, for example) for the purpose of high integration. Just after a Ta2O5 thin film is produced, the characteristics are poor. Therefore methods for improving the characteristics such as heat treatment have been proposed. The following examples have been proposed:
a process for producing a Ta2O5 film of high quality by thermal oxidation to a laminated film of Ta2N and Ta (Japanese Patent Application Laid-Open No.SHO62-136035);
a process for executing heat treatment in order to densify a Ta2O5 film by ion implantation of titanium after the film is produced (Japanese Patent Application Laid-Open No.HEI 4-359557);
a process for executing heat treatment in order to densify a Ta2O5 film by ion implantation of fluorine after the film is produced (Japanese Patent Application Laid-Open No.SHO64-82557); and
a process for producing a Ta2O5 film by thermal oxidation after a Ta film is converted into amorphous (Japanese Patent Application Laid-Open No.SHO60-5531).
However, in any case described above, a physical property of the film in an atomic bonding level and its changes according to the post processes have not been comprehended exactly, and therefore these methods are just experiential ones. That is because the Ta2O5 in an atomic bonding state (crystal structure) is extremely complex, so that there is no means to evaluate the quality of the film easily, and that there is no character to control it.
The first problem is that although high permittivity and low leak current are required even in a thin film of under 10 nm thickness; it is impossible to control and produce a stable film having high quality. This is because a physical property which is, different from a bulk material is shown when Ta2O5 is thinned down and is used as a capacitative insulating film.
The second problem is that although some improvements in the characteristics are made by heat treatment and so forth, in order to solve the problem, these methods are just experiential ones because a physical property of the film and its changes have not been comprehended exactly. This is because Ta2O5 in an atomic bonding state (crystal structure) is extremely complex, so that there is no means to evaluate the quality of the film easily, and that there is no character to control it.
It is therefore an object of the present invention to provide a manufacturing method of a semiconductor device, in which a Ta2O5 thin film, which has high permittivity and low leak current, is employed for a capacitative insulating film.
Another object of the present invention is to provide a method for monitoring an atomic bonding state in a film, which is for the purpose of controlling quality of a Ta2O5 film.
First, for achieving the objects mentioned above, a Ta2O5 thin film that has double bond (Taxe2x95x90O) of Ta and O (oxygen) is employed for a capacitative insulating film. By measuring a transmission infrared absorption spectrum of a Ta2O5 thin film using Fourier Transform Infrared Spectroscopy (FTIR), it is monitored whether absorption peak that appears in 2340 cmxe2x88x921 exists or not and it is large or small. This technique is realized because a new fact has been brought to light that the existence of the peak described above is discovered and the peak is the absorption peak which appears by stretching vibration of Taxe2x95x90O. As a concrete process, there are Rapid Thermal Anneal (RTA) in oxygen and UV/O3 (Ultra Violet-Ozone) treatment at a suitable temperature and in suitable time, for example.
Second, a Ta2O5 thin film, wherein an abundance ratio of oxygen in a three coordinate bonding (triple bonding) state is large, is employed for a capacitative insulating film. By using FTIR, an intensity ratio of each double peak which appears around 510 cmxe2x88x921 and 570 cmxe2x88x921 is measured, so that the Ta2O5 film whose ratio (510/570) is larger than another one is used as a character in order to improve the quality of a film. This technique is realized because a new fact has been brought to light that all of the peak appears by an asymmetric stretching vibration mode of three coordinate oxygen (Oxe2x89xa13Ta).
By using a Ta2O5 film which has Taxe2x95x90O bond or that of which an abundance ratio of oxygen in a three coordinate bonding state is large as a capacitative insulating film, the capacitance characteristics of leak electric current and reduced coating thickness etc. are improved. First, this is because Taxe2x95x90O double bond whose bonding strength is very strong is produced by dissociation of organic impurities in CVD raw gas over 500xc2x0 C. and atomic oxygen bonding to the vacant site. Second, this is because the quality of the film becomes strong by producing more stable three coordinate bond than unstable two coordinate bond (Taxe2x80x94Oxe2x80x94Ta) in the complex crystalline structure of Ta2O5.
After measuring Taxe2x95x90O peak or an intensity ratio of the 510/570 peak in a Ta2O5 thin film which has been processed by a variety of heat treatment, in comparison with these capacitance characteristics, there is an evident relevance. Therefore, the present invention is as follows:
(1) a semiconductor device wherein an Amorphous Ta2O5 thin film having double bond (Taxe2x95x90O) of Ta with O (oxygen) which is formed on a semiconductor substrate is a capacitative insulating film;
(2) a semiconductor device wherein a polycrystal or single crystal Ta2O5 thin film having double bond (Taxe2x95x90O) of Ta with O (oxygen) which is formed on a semiconductor substrate is a capacitative insulating film;
(3) a semiconductor device wherein a Ta2O5 thin film in which an abundance ratio of oxygen in a three coordinate bonding state is large, which is formed on a semiconductor substrate, is a capacitative insulating film;
(4) a manufacturing method of a semiconductor device comprising steps of:
adhering a Ta2O5 thin film on an N-type silicon substrate by chemical vapor deposition; and
forming an amorphous Ta2O5 thin film having double bond (Taxe2x95x90O) of Ta with O (oxygen) by executing Rapid Thermal Anneal at 300-600xc2x0 C. to the Ta2O5 thin film under an oxidized atmosphere;
(5) the manufacturing method of a semiconductor device as described in (4), wherein the Rapid Thermal anneal is executed while infrared absorption peak of 2340 cmxe2x88x921 in the Ta2O5 thin film is measured;
(6) the manufacturing method of a semiconductor device as described in (5), wherein a state of distribution of Taxe2x95x90O bond in the Ta2O5 thin film is monitored by the measurement;
(7) the manufacturing method of a semiconductor device as described in (4), wherein the Rapid Thermal Anneal is executed within 1 second-4 hours;
(8) a manufacturing method of a semiconductor device comprising steps of:
adhering a Ta2O5 thin film on an N-type silicon substrate by chemical vapor deposition; and
forming a polycrystal or single crystal Ta2O5 thin film having double bond (Taxe2x95x90O) of Ta with O (oxygen) by executing Rapid Thermal Anneal at 700-1000xc2x0 C. to the Ta2O5 thin film under an oxidized atmosphere;
(9) the manufacturing method of a semiconductor device as described in (8), wherein the Rapid Thermal Anneal is executed while infrared absorption peak of 2340 cmxe2x88x921 in the Ta2O5 thin film is measured;
(10) the manufacturing method of a semiconductor device as described in (9), wherein a state of distribution of Taxe2x95x90O bond in the Ta2O5 thin film is monitored by the measurement;
(11) the manufacturing method of a semiconductor device as described in (8), wherein the Rapid Thermal Anneal is executed within 1 second-4 hours;
(12) a manufacturing method of a semiconductor device comprising steps of:
adhering a Ta2O5 thin film on an N-type silicon substrate by chemical vapor deposition; and
forming a Ta2O5 thin film in which an abundance ratio of oxygen in a three coordinate bonding state is large by executing Rapid Thermal Anneal at 700-1000xc2x0 C. to the Ta2O5 thin membrane under an oxidized atmosphere;
(13) the manufacturing method of a semiconductor device as described in (12), wherein the Rapid Thermal Anneal is executed while an intensity ratio of infrared absorption peak of 510 cmxe2x88x921 and 570 cmxe2x88x921 in the Ta2O5 thin film is measured;
(14) the manufacturing method of a semiconductor device as described in (13), wherein a state of distribution of Taxe2x95x90O bond in the Ta2O5 thin film is monitored by the measurement;
(15) the manufacturing method of a semiconductor device as described in (12), wherein the Rapid Thermal Anneal is executed within 1 second-4 hours; and
(16) a manufacturing method of a semiconductor device comprising steps of:
forming a barrier film on an N-type silicon substrate by rapid nitriding and adhering the first Ta2O5 thin film on the barrier film by chemical vapor deposition;
executing UV/O3 treatment to the first Ta2O5 thin film at 300-550xc2x0 C. and furnace heat treatment to it at 700-1000xc2x0 C. under an oxidized atmosphere;
adhering the second Ta2O5 thin film on the first Ta2O5 thin film by chemical vapor deposition; and
executing UV/O3 treatment to the second Ta2O5 thin film at 300-550xc2x0 C. and furnace heat treatment to it at 700-1000xc2x0 C. under an oxidized atmosphere.